U.S. patent number 7,159,487 [Application Number 10/606,931] was granted by the patent office on 2007-01-09 for method for making a polycrystalline diamond insert drill bit body.
This patent grant is currently assigned to Smith International, Inc.. Invention is credited to Graham Mensa-Wilmot, Tommy G. Ray, Youhe Zhang.
United States Patent |
7,159,487 |
Mensa-Wilmot , et
al. |
January 9, 2007 |
Method for making a polycrystalline diamond insert drill bit
body
Abstract
A method for forming a drill bit body is disclosed which
comprises infiltrating powdered tungsten carbide with a binder
alloy in a mold. The mold has therein at least one displacement
adapted to form a mounting pad for a cutting element. The
displacement comprises a substantially cylindrical body having a
diameter selected to substantially conform to a radius of the
cutting element and a projection adapted to form a relief groove
under a position of a diamond table in the cutting element when the
cutting element is mounted on the pad. The width of the relief
groove is selected so that the relief groove extends back from an
outer surface of the bit body at least about 40 percent of that
portion of a thickness of the diamond table which does not extend
past the outer surface.
Inventors: |
Mensa-Wilmot; Graham (Houston,
TX), Ray; Tommy G. (Houston, TX), Zhang; Youhe
(Houston, TX) |
Assignee: |
Smith International, Inc.
(Houston, TX)
|
Family
ID: |
24802545 |
Appl.
No.: |
10/606,931 |
Filed: |
June 26, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040118616 A1 |
Jun 24, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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09697789 |
Oct 26, 2000 |
6823952 |
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Current U.S.
Class: |
76/108.2;
175/432 |
Current CPC
Class: |
E21B
10/43 (20130101); E21B 10/55 (20130101) |
Current International
Class: |
B21K
5/02 (20060101); E21B 10/52 (20060101) |
Field of
Search: |
;76/108.2
;175/432,428,434,426 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Payer; Hwei-Siu
Attorney, Agent or Firm: Osha Liang LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional application of U.S. patent
application Ser. No. 09/697,789 entitled "STRUCTURE FOR
POLYCRYSTALLINE DIAMOND INSERT DRILL BIT BODY AND METHOD FOR
MAKING", filed Oct. 26, 2000, now U.S. Pat. No. 6,823,952.
Claims
What is claimed is:
1. A method for forming a drill bit body, comprising: selecting at
least one displacement, wherein the at least one displacement
comprises: a substantially cylindrical body having a diameter
selected to substantially conform to the radius of a cutting
element having a diamond table; and a projection adapted to form a
relief groove in the drill bit body, wherein the relief groove is
positioned under the diamond table of the cutting element when the
cutting element is mounted on a mounting pad formed in the drill
bit body, wherein a width of the relief groove is selected so that
the relief groove extends back from an outer surface of the drill
bit body at least about 40 percent of that portion of a thickness
of the diamond table which does not extend past the outer surface
of the drill bit body; inserting the displacement into a mold; and
infiltrating powdered tungsten carbide with a binder alloy in the
mold to form from said displacement said mounting pad and said
relief groove in the drill bit body.
2. The method as defined in claim 1 wherein the step of selecting
the at least one displacement comprises selecting a castable
material formed into a single body for said displacement.
3. The method as defined in claim 1 wherein the step of selecting
the displacement comprises extending the projection past an
external surface of the displacement by about 0.025 inches.
4. A method for forming a drill bit body, comprising: selecting at
least one displacement, wherein the at least one displacement is a
single component comprising: a substantially cylindrical body
having a diameter selected to substantially conform to the radius
of a cutting element having a diamond table; and a projection
adapted to form a relief groove in the drill bit body, wherein the
relief groove is positioned under the diamond table of the cutting
element when the cutting element is mounted on a mounting Dad
formed in the drill bit body; inserting the displacement into a
mold; and infiltrating powdered tungsten carbide with a binder
alloy in the mold to form from said displacement said mounting pad
and said relief groove in the drill bit body.
5. The method as defined in claim 4 wherein the step of selecting
the displacement comprises having the relief groove with a depth of
about 0.025 inches.
6. The method as defined in claim 4 wherein the step of selecting
the displacement comprises extending the relief groove back from an
outer surface of the blade at least about 40 percent of that
portion of a thickness of the diamond table which does not extend
past the outer surface.
Description
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF INVENTION
1. Field of the Invention
The invention is related to the field of fixed cutter bits used to
drill weilbores through earth formations. More specifically, the
invention is related to structures for, and methods for making,
alloy bodies for polycrystalline diamond compact cutter drill
bits.
2. Background Art
Fixed cutter drill bits known in the art include polycrystalline
diamond compact (PDC) bits. The typical PDC bit includes a bit body
which is made from powdered tungsten carbide infiltrated with a
binder alloy within a suitable mold form. The particular materials
used to form PDC bit bodies are selected to provide adequate
toughness, while providing good resistance to abrasive and erosive
wear. The cutting elements used on these bits are typically formed
from a cylindrical tungsten carbide "blank" or substrate. A diamond
"table" made from various forms of natural and/or synthetic diamond
is affixed to the substrate. The substrate is then generally brazed
or otherwise bonded to the bit body in a selected position on the
surface of the body.
The materials used to form PDC bit bodies, in order to be resistant
to wear, are very hard and are therefore difficult to machine.
Therefore, the selected positions at which the PDC cutting elements
are to be affixed to the bit body are typically formed
substantially to their final shape during the bit body molding
process. A common practice in molding PDC bit bodies is to include
in the mold at each of the to-be-formed cutter mounting positions,
a shaping element called a "displacement". A displacement is
generally a small cylinder made from graphite or other heat
resistant material which is affixed to the inside of the mold at
each of the places where a PDC cutter is to be located on the
finished drill bit. The displacement forms the shape of the cutter
mounting positions during the bit body molding process. See, for
example, U.S. Pat. No. 5,662,183 issued to Fang for a description
of the infiltration molding process using displacements.
PDC bits known in the art have been subject to fracture failure of
the diamond table, and/or separation of the diamond table from the
substrate during drilling operations. One reason for such failures
is compressive contact between the exterior of the diamond table
and the proximate surface of the bit body under drilling loading
conditions. One solution to this problem known in the art is to
mount the cutting elements so that substantially all of the
thickness of the diamond table is projected outward past the
surface of the bit body. While this solution does reduce the
incidence of diamond table failure, having the diamond tables
extend outwardly past the bit body can cause erratic or turbulent
flow of drilling fluid past the cutting elements on the bit. This
turbulent flow has been known to cause the cutter mounting to
erode, and to cause the bonding between the cutters and the bit
body to fail, among other deficiencies in this type of PDC bit
configuration. It is preferable to have the PDC cutters mounted so
that they are substantially flush with the outer surface of the
mounting position on the bit body.
What is needed is a structure for a PDC bit body which reduces
diamond table failure, while retaining the benefits of flush
mounting of the cutters on the bit body.
SUMMARY OF INVENTION
One aspect of the invention is a method for forming a drill bit
body which comprises infiltrating powdered tungsten carbide with a
binder alloy in a mold. The mold has therein at least one
displacement adapted to form a mounting pad for a cutting element.
The displacement comprises a substantially cylindrical body having
a diameter selected to substantially conform to a radius of the,
cutting element and a projection adapted to form a relief groove
under a position of a diamond table forming part of the cutting
element when the cutting element is mounted on the pad. The width
of the relief groove is selected so that the relief groove extends
back from an outer surface of the bit body at least about 40
percent of that portion of a thickness of the diamond table which
does not extend past the outer surface.
Another aspect of the invention is a drill bit body comprising a
main body having at least one blade formed therein, and at least
one cutting element mounting pad formed on the at least one blade.
The mounting pad is adapted to receive therein a substrate of a
cutting element. The mounting pad has a relief groove therein under
a position of a diamond table in the cutting element when the
cutting element is mounted on the pad. The width of the relief
groove is selected so that the relief groove extends back from an
outer surface of the blade at least about 40 percent of that
portion of a thickness of the diamond table which does not extend
past the outer surface.
Other aspects and advantages of the invention will be apparent from
the following description and the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a side view of one example of a displacement made
according to the invention
FIG. 2 shows an end view of a displacement such as shown in FIG.
1.
FIG. 3 shows a cross section of a drill bit body having a cutting
element mounted on a pad made according to the invention.
FIG. 4 shows an example of a PDC drill bit made according to the
invention.
DETAILED DESCRIPTION
A matrix drill bit body for a fixed cutter bit according to the
various embodiments of the invention can be made from powdered
tungsten carbide infiltrated with a binder alloy in a suitably
shaped mold or other form. See, for example, U.S. Pat. No.
5,662,183 issued to Fang, incorporated herein by reference. In
particular, the bit body forming process described in the Fang '183
patent includes insertion of plugs, called "displacements," in
locations about the bit body on which cutting elements are to be
mounted to the finished bit body. The locations at which cutting
elements are to be mounted are referred to for convenience herein
as "mounting pads".
In a drill bit body made according to the invention, displacements
are inserted into the mold during the body forming process to
produce mounting pads for the cutting elements. An example of a
displacement according to one aspect of the invention is shown in
FIG. 1. The displacement 10 in this embodiment is a substantially
cylindrical body having a selected length indicated by L, a
diameter indicated by D and on one end, a projection 12 having a
selected width W. The length L and diameter D are selected to
provide a mounting pad (not shown in FIG. 1) on the finished bit
body (not shown in FIG. 1) having dimensions suitable to mount a
selected cutting element (not shown in FIG. 1). Typically the
cutting element (not shown in FIG. 1) affixed to the mounting pad
will be a polycrystalline diamond compact insert. The projection 12
in this embodiment has a substantially cylindrical shape and
extends laterally past the exterior surface 10A of the main body of
the displacement 10 by about 0.025 inches (0.63 mm) in this
embodiment. The displacement 10 is affixed to the mold (not shown
in FIG. 1) so that the mounting pad is formed to have a recess or
relief groove (not shown in FIG. 1) positioned under a diamond
table forming part of the cutting element affixed to the mounting
pad. The position of the relief groove and diamond table will be
further explained.
The example displacement is shown in an end view in FIG. 2, where
the shape and lateral extent of the projection 12 can be seen. In
this embodiment, the projection 12 has a primary surface 12A which
extends laterally from the surface (10A in FIG. 1) of the
displacement by about 0.025 inches (0.63 mm) and is substantially
concentric with the surface (10A in FIG. 1) of the displacement 10
between points A and B. Transition surfaces, formed between
endpoint A and point C1, and endpoint B and point C2 on the
circumference of the displacement 10, can be formed to gradually
adjust the radius of the exterior surface of the projection 12 to
match the radius of the main surface 10A of the displacement 10.
Typically, points C1 and C2 will be spaced about 180 degrees apart
so that the relief groove formed in the mounting pad will extend
about 180 degrees. Other angular spacings of points C1 and C2, and
endpoints A and B will also work with the invention, however.
The displacement 10 may be made from graphite or any other suitable
material used for molding of matrix bodies. Using casting or cold
pressing methods can be advantageous by enabling forming the
displacement 10, including the projection 12 thereon, as a single
piece.
As described in the Fang '183 patent, after the displacements are
inserted into selected locations in the mold, powdered tungsten
carbide is inserted into the mold and is then infiltrated with a
binder alloy. Typically, the bit body thus formed will include
"blades", each of which includes one or more of the mounting pads
formed by the displacements.
A blade portion of a bit body formed using a displacement such as
shown in FIGS. 1 and 2, is shown in cross section in FIG. 3. The
blade 24 includes thereon a mounting pad 25 having the shape of the
displacement (10 in FIG. 1). As previously explained, the radius of
the mounting pad 25 is determined by the diameter (D in FIG. 1) of
the displacement. Typically, this radius is selected to match the
radius of the cutting element mounted thereon. As shown in FIG. 3,
a relief groove 26 is formed in the mounting pad 25 by having
placed the displacement (10 in FIG. 1) in the mold so that the
projection (12 in FIG. 1) was positioned outward and downward with
respect to the blade 24. Shown mounted in the pad 25 is a cutting
element consisting of a diamond table 20 affixed to a substrate 22.
Typically, the substrate 22 is formed from tungsten carbide or
similar hard material. The diamond table 20 can be formed in any
manner known in the art for making diamond cutting surfaces for
fixed cutter drill bits. The cutting element is typically bonded to
the blade 24 by brazing the substrate 22 to the blade 24. In this
embodiment, the diamond table 20 extends longitudinally past the
surface of the blade 24 by an amount shown at E. The diamond table
20 has a thickness Z which is selected based on the diameter of the
cutting element and the expected use of the particular drill bit,
among other factors. In the invention, it has been determined that
diamond table breakage is reduced efficiently when the width X of
the relief groove 26 is selected so that the groove 26 extends back
from the surface of the blade 24 at least about 40 percent of that
portion (Z-E) of the thickness Z of the diamond table which does
not extend past the edge of the blade 24. Expressed mathematically:
X/(Z-E)..gtoreq..0.40
In the example shown in FIG. 3, the diamond table thickness Z is
about 0.110 inches (2.8 mm) and an extension E of the outer surface
of the diamond table 22 past the edge of the blade 24 is about
0.040 inches (1 mm). The width X of the relief groove 26 should
therefore be greater than or equal to about 0.028 inches (0.7 mm).
As previously explained, the width X of the relief groove 26 can be
selected by appropriate choice of the width (W in FIG. 1) of the
projection (12 in FIG. 1) on the displacement.
Preferably, the relief groove 26 has a depth of about 0.025 inches
(0.6 mm). As previously explained, this depth can be formed in the
bit body at the position of any or all of the mounting pads 24 by
forming the displacement (10 in FIG. 2) so that the projection (12
in FIG. 2) extends past the main surface (10A in FIG. 1) by about
0.025 inches (0.6 mm).
In a drill bit body made according to the invention, a displacement
such as shown in FIGS. 1 and 2 is positioned in the mold at each
place where a cutting element is to be mounted. Each mounting pad
thus formed in the bit body will have a relief groove such as shown
in FIG. 3. An example of a PDC cutter drill bit made according to
the invention is shown in FIG. 4. The bit body 100 has thereon a
plurality of blades 110. Each of the blades 110 has mounted thereon
on mounting pads (shaped according to FIG. 3) a PDC cutting element
112. Each PDC cutting element 112 includes a diamond table 113
affixed to a tungsten carbide substrate 114. The bit body 100
includes suitably positioned nozzles or "jets" 120 to discharge
drilling fluid in selected directions and at selected rates of
flow.
The foregoing embodiments of the invention are directed to bit
bodies being formed by infiltrating powdered tungsten carbide with
a binder alloy in a suitable mold. In other embodiments of the
invention, a bit body such as shown at 100 in FIG. 4 can be made
from steel or other alloy which can be machined or otherwise cut
and finished formed using conventional machining and/or grinding
equipment. In this embodiment, a bit body "blank" is rough formed
such as by casting, or forging, and is finished machined to include
at least one of the blades 110 having mounting pads for cutting
elements. In this embodiment, and referring again to FIG. 3, the
mounting pads 25 are formed by grinding or machining to include a
relief groove 26. In embodiments of the invention which have a bit
body that is finish machined from a bit body blank, the relief
grooves 26 may have any suitable width, but preferably have about
the same width as in the previous embodiments including the
infiltration-molded bit body.
A drill bit made according to the invention can have reduced
breakage of diamond tables on the cutting elements as compared with
prior art drill bits made without such relief grooves. Such bits
may provide increased bit life and reduced drilling costs.
While the invention has been described with respect to a limited
number of embodiments, those skilled in the art will appreciate
that other embodiments can be devised which do not depart from the
scope of the invention as disclosed herein. Accordingly, the scope
of the invention should be limited only by the attached claims.
* * * * *